Polymer-based spherical powder preparation device and preparation process

ABSTRACT

A polymer-based spherical powder preparation device and preparation process are disclosed. The preparation device comprises a mill milling system and an inductively coupled plasma powder spheroidization system. The mill milling system of the preparation device can achieve ultra-fine grinding of the material at room temperature by applying strong extrusion, shear and circumferential stress to the material; and the inductively coupled plasma powder spheroidization system using high temperature plasma as high temperature heat source, the polymer powder can be heated uniformly, and the melting and cooling rate is fast, so the spheroidization can be completed in a short time. The preparation process of polymer based spherical powder was integrated and continuously produced by the preparation device.

BACKGROUND Technical Field

The present invention belongs to the field of polymer materials, andspecifically relates to a polymer-based spherical powder preparationdevice and preparation method, especially preparation of raw materialssuitable for a selective laser sintering technology.

Related Art

As an important 3D printing technology, a selective laser sintering(SLS) technology is an advanced manufacturing method which has beendeveloped rapidly in recent years based on a discrete/stackingprinciple. According to the SLS technology, powder materials areselectively melted under heat action of lasers and stacked layer bylayer on the basis of a CAD model to form a final part. Compared withtraditional processing methods, SLS processing mainly has the technicaladvantages of free forming and overall manufacturing, thus can be usedto produce parts with arbitrarily complex structures. Therefore,customized production of complex parts is achieved.

Raw materials for SLS processing are powder materials, mainly includingmetal materials, ceramic materials and polymer materials. Compared withother materials, polymer materials have the advantages of low density,low costs and easy modification, processing and post-treatment, and canmeet individual needs under different application conditions. Therefore,the polymer materials are the most widely used SLS materials. Based on aunique processing process, the SLS technology has high performancerequirements for polymer materials. Under such requirements, warping anddeformation of SLS parts can be effectively prevented through a widesintering window, and proper particle size distribution and high bondingstrength are the key to obtaining good parts. In addition, highflowability and bulk density of polymer powder materials are also theguarantee for obtaining SLS parts with high density, high mechanicalstrength and high dimensional precision.

Polymer materials have an important position in selective lasersintering materials and broad application prospects. So deep researcheson application of polymer powder materials in selective laser sinteringhave been conducted by scholars at home and abroad. Particle shapes ofpolymer powder materials have a significant effect on performance ofparts and are related to preparation methods. At present, processing andpreparation methods of polymer powder for selective laser sinteringmainly include a cryogenic pulverization method, a solvent precipitationmethod, a spray drying method and the like. These methods have differentadvantages, and can prepare SLS polymer powder materials with certainparticle size distribution and regular shapes. But these methods alsohave certain defects: the cryogenic pulverization method has simpleoperation, but poor powder mixing effect and powder form. Powderprepared by using the solvent precipitation method is uniform in sizeand mixing, but the operation is complicated, and the productionefficiency is low. The spray drying method is high in consumption oforganic solvents, which may pollute the environment.

SUMMARY

In order to solve the defects or problems in the related art, thepresent invention provides a polymer-based spherical powder preparationdevice and preparation method. With the preparation device, integratedand continuous production of a polymer-based spherical powder in apreparation method is achieved, and the preparation method is greatlyimproved, so that a polymer-based spherical powder material withexcellent performance and applicable to the SLS field is prepared, andcan be produced in a large scale at the same time.

In order to achieve the objectives above, the present invention isimplemented by adopting a technical solution comprising the followingtechnical features.

A polymer-based spherical powder preparation device includes a millmilling system and an inductively coupled plasma powder spheroidizationsystem.

The mill milling system includes a feeding member, a mill cavity cover,a fixed mill, a rotating mill, a rotating bearing, a transmissiondevice, a motor and a liquid medium temperature adjustment system. Thefixed mill and the rotating mill are fixed in the mill cavity cover, therotating mill is fixedly connected to the rotating bearing, and thetransmission device is driven by the motor to drive the rotating bearingto rotate, thereby driving the rotating mill to rotate. The fixed milland the rotating mill are also provided with the liquid mediumtemperature adjustment system, the liquid medium temperature adjustmentsystem realizes temperature adjustment of the fixed mill and therotating mill by introducing a liquid medium into the fixed mill and therotating mill, and the entire mill milling system is of a closed type.

The inductively coupled plasma powder spheroidization system includes aninductively coupled plasma generator, a cooling and shaping chamber, acollection chamber, a gas supply device, a high-frequency power supplyand a vacuum pumping device, and the inductively coupled plasmagenerator, the cooling and shaping chamber and the collection chamberare communicated with one another.

The inductively coupled plasma generator includes a feeding pipe, areaction gas pipe, a protective gas pipe, an induction coil, a moltenmaterial spray head and a generator housing, the reaction gas pipe isarranged in the protective gas pipe, one end of the feeding pipe isclosely connected to a discharging end of the mill milling system, theother end of the feeding pipe penetrates through the reaction gas pipeand extends into the protective gas pipe, the induction coil is arrangedaround an outside of the protective gas pipe, and the reaction gas pipedoes not extend into a surrounding setting surface of the inductioncoil. The molten material spray head is arranged at a tip of the end,close to the induction coil, of the protective gas pipe. The reactiongas pipe, the protective gas pipe, the induction coil and the moltenmaterial spray head are all closely fixed in the generator housing, andthe inductively coupled plasma generator is communicated with thecooling and shaping chamber through the molten material spray head.

The cooling and shaping chamber includes a plurality of high-pressuregas spray heads and a cooling and shaping chamber housing, thehigh-pressure gas spraying heads are arranged around a cross section ofthe cooling and shaping chamber housing at equal distances, nozzles ofthe high-pressure gas spraying heads all face the same position in thecooling and shaping chamber housing, and the position is located on acentral axis of a nozzle of the molten material spray head.

The collection chamber includes a condensed water inlet pipe, a slurryoutlet and a collection chamber housing, and the collection chamberhousing is communicated with the cooling and shaping chamber housing.

The gas supply device includes a reaction gas inlet pipe with one endcommunicated with the reaction gas pipe and a protective gas inlet pipewith one end communicated with the protective gas pipe, and the otherends of the reaction gas inlet pipe and the protective gas inlet pipeare communicated with the reaction gas pipe and the protective gas piperespectively.

The vacuum pumping device is communicated with an inside of the coolingand shaping chamber housing.

Further, The high-frequency power supply is electrically connected tothe induction coil, and a high-frequency power supply with an outputfrequency of 3±0.5 MHz is used.

Further, the mill milling system also includes a hydraulic machine, thefixed mill and the rotating mill are fixedly connected to the hydraulicmachine, and the milling surface spacing or pressure between the fixedmill and the rotating mill is adjusted by using the hydraulic machine.

Further, the liquid medium temperature adjustment system is liquidmedium channels separately arranged in the fixed mill and the rotatingmill and a corresponding liquid medium circulation device. Preferably,the rotating bearing is separately provided with a liquid medium inletand a liquid medium outlet, and the liquid medium inlet and the liquidmedium outlet are communicated with the liquid medium channel in therotating mill.

Usually, the discharging end, closely connected to one end of thefeeding pipe, of the mill milling system is determined by a dischargingport according to different types of milling surfaces of the used fixedmill and the rotating mill. For example, when the same fixed mill androtating mill in the prior patent “Solid Phase Power Chemical Reactor”(China Patent No. ZL95111258.9, Publication No. CN1130545A) of theapplicant are used, the discharging end is arranged around edges of thetwo mills. A closed groove surrounding the mills can be designed bythose skilled in the art according to the discharging end above tocollect milled materials, and transfer the materials into the feedingpipe. The design of the discharging end structure above is conventionalknowledge in the field of milling processing or prior art.

Preferably, the feeding pipe is also covered with a condensed watersleeve. Usually, the condensed water sleeve is communicated with acondensed water circulation system to exchange condensed water. Furtherpreferably, the feeding pipe is also provided with a temperaturemeasuring device.

Preferably, a central axis of the reaction gas pipe overlaps with acentral axis of the protective gas pipe, and one ends of the reactiongas pipe and the protective gas pipe are flush and fixed in thegenerator housing. The reaction gas pipe is a straight pipe with alength of 50-80 mm and a nozzle diameter of 30-40 mm, and the protectivegas pipe is a straight pipe with a length of 300-400 mm and a nozzlediameter of 50-60 mm.

Preferably, in order to improve the melting effect of the inductivelycoupled plasma generator on the polymer-based powder, a diameter of thefeeding pipe is 10-15 mm, the other end of the feeding pipe penetratesthrough the reaction gas pipe and extends into the protective gas pipe,and the nozzle of the feeding pipe extending into the protective gaspipe is 20-50 mm away from the reaction gas pipe, so that thepolymer-based powder directly enters a target area of a plasma torchthrough the feeding pipe, and a temperature field of the target area is100-500° C.

Preferably, in order to increase the flow rate of the molten materialsin the plasma torch, shorten the residence time of the materials in theplasma torch and prevent polymers from decomposing and carbonizing dueto long residence time, a diameter of the protective gas pipe is reducedfrom 50-60 mm to 10-15 mm which is the same as a nozzle diameter of themolten material spray head, and a flow rate of the materials isincreased by reducing a width of a flow channel. The nozzle of themolten material spray head overlaps with a central axis of theprotective gas pipe, the molten material spray head forms a convexstructure toward the outside of the protective gas pipe, and the nozzleis 10-30 mm away from the protective gas pipe.

A plurality of the high-pressure gas spray heads are arranged around across section of the cooling and shaping chamber housing at equaldistances, nozzles of the high-pressure gas spraying heads all face thesame position in the cooling and shaping chamber housing, the pressureof introduced gas is maintained the same when the high-pressure gasspraying heads are used, so as to quickly cool the polymer-based powderafter plasma melting, prevent the polymer-based powder from degradingand oxidizing in a high-temperature melting state and make physical andchemical properties of the polymer-based powder remain unchanged. At thesame time, the pressure of gas introduced into the high-pressure gasspray heads which are arranged around the cross section of the coolingand shaping chamber housing at equal distances is maintained the same, alow-temperature cooling area is formed at a lower end of the moltenmaterial spray head, and a flow direction of carrier gas discharged fromthe molten material spray head is not changed by the high-pressure gasspray heads which are arranged at equal distances, so that thepolymer-based powder is cooled and shaped without collision, theprepared polymer-based powder has no agglomeration phenomenon, andsurfaces of particles are smooth. Preferably, there are 8 high-pressuregas spray heads, the cross section of the cooling and shaping chamberhousing is circular, the 8 high-pressure gas spray heads are arrangedaround the circular cross section of the cooling and shaping chamberhousing at equal distances, and the nozzles all face a circular centerof the circular cross section.

The vacuum pumping device is communicated with an inside of the coolingand shaping chamber housing, the inductively coupled plasma generator,the cooling and shaping chamber and the collection chamber arecommunicated with one another, one end of the feeding pipe in theinductively coupled plasma generator is closely connected to thedischarging end of the mill milling system, and condensed water isintroduced into the collection chamber and floods the slurry outlet.Therefore, the inductively coupled plasma generator, the cooling andshaping chamber and the collection chamber which are communicated withone another constitute a closed system. When the vacuum pumping devicecommunicated with the inside of the cooling and shaping chamber housingis in operation, a negative pressure environment is formed inside theclosed system, and therefore, no additional power source or operation isneeded for transporting the materials in the feeding pipe.

Preferably, the generator housing, the cooling and shaping chamberhousing and the collection chamber housing are connected to one anotherand integrally formed, a double-layer water-cooled stainless steelstructure is adopted, and a cooling water inlet and outlet is formed inan outside surface.

Generally speaking, in addition to the structural features and technicalparameters defined by the present invention, an inductively coupledplasma powder spheroidization device in the ceramic field can be takenas a reference for other technical features and implementation methodsof the inductively coupled plasma powder spheroidization system, such asthe prior patent “A Device and Method for Generating Inductively CoupledThermal Plasma under Low Pressure” (CN201510385291.5).

It is worth noting that although the inductively coupled plasma powderspheroidization system is widely used in the ceramic field, ceramicshave a melting point much higher than that of polymer-based powders andother characteristics, and an inductive plasma torch is a temperaturefield with dozens to tens of thousands of Celsius degrees, the meltingpoint of ceramics is often thousands of Celsius degrees, and thespheroidization treatment temperature is thousands to tens of thousandsof Celsius degrees. The melting point of polymers is mostly 100-400° C.,the decomposition temperature is mostly 200-500° C., and thespheroidization treatment temperature is higher than the melting pointand lower than the decomposition temperature. Therefore, the technicalsolution of the present invention is developed and designed by theinventor of the present invention according to different characteristicsof the above materials.

A preparation method for preparing polymer-based spherical powder byusing the preparation device includes the following steps:

(1) milling: putting polymer-based particles into the preparation devicethrough a feeding member, and setting process parameters for the millmilling system as follows: a milling pressure is 10-15 MPa, a rotatingspeed of a rotating mill is 20-50 r/min, and a temperature of coolingwater is 0-20° C.;

(2) spheroidization: introducing reaction gas and protective gas througha reaction gas inlet pipe and a protective gas inlet pipe respectively,introducing high-pressure gas into a high-pressure gas spray head forspraying, and setting process parameters for a inductively coupledplasma powder spheroidization system as follows: a reaction gas flowrate is 1-1.5 m³/h, a protective gas flow rate is 1-1.5 m³/h, a voltageof a high-frequency power supply is 6000-7000 V, an anode current is5-10 A, a frequency is 3±0.5 MHz, a flow rate of molten materials at anozzle is maintained at 3-5 V/s, and a gas pressure in a cooling andshaping chamber is maintained at 0.02-0.08 MPa;

(3) collection: introducing condensed water through a condensed waterinlet formed in a collection chamber, and collecting a slurry productflowing out of the slurry outlet;

(4) post-treatment: filtering, drying and sieving the collected slurryproduct to obtain a polymer-based spherical powder.

The polymer-based material is usually a thermoplastic polymer-basedmaterial which can be used for 3D printing. In order to betterillustrate the present invention, the polymer-based material ispreferably nylon, polyvinylidene fluoride, polyether-ether-ketone,polystyrene or polyurethane, or a composite material with the preferredpolymer-based material above as a main component.

Preferably, in the spheroidization step, a temperature in the feedingpipe is controlled to be 40-70° C. The temperature can be controlled bycombining condensed water circulation and temperature measurement.

The reaction gas is preferably argon, and the protective gas ispreferably argon or nitrogen.

The high-pressure gas is preferably inert gas argon, and an introducedgas pressure is 1-2 MPa.

The present invention provides a continuous production device includinga milling system, a spheroidization system and a collection system. In apreferred technical solution, according to different physical propertiesof materials, the pressure between the mills can be adjusted by using ahydraulic machine to achieve the best milling effect. Since a negativepressure environment is formed inside the apparatus, the materials aredriven by airflow to enter the milling system conveniently and quicklywithout manual addition. With the design and improvement above, theproduction efficiency of the apparatus is greatly improved, the outputcan reach 10-15 kg/h, continuous and batch production of allthermoplastic polymer spherical powder is realized, and there is no needto adjust process parameters according to polymer types. According tothe production device, inert gas is used as a dispersion medium, and nodispersant is needed, so that the production process is environmentallyfriendly and clean. The powder only has physical changes in aspheroidization process, so that chemical properties of the obtainedspherical powder are the same as those of original polymers, and theproduct property is stable.

The polymer-based spherical powder prepared according to the technicalsolution of the present invention has a sphericity of 97% or above, asmooth particle surface with no wrinkles and burrs, an average particlesize of 90-100 μm, narrow and normal particle size distribution, and ahalf-peak width of 100-110 μm. In the prepared polymer-based sphericalpowder, a sintering window of PA11 spherical powder is 15° C., asintering window of PVDF spherical powder is 18° C., the powderflowability is high, and a stacking angle is 23-27°.

The technical route of the present invention is mature, stable andreliable, and the polymer-based spherical powder preparation devicehaving a powder preparation function and a powder spheroidizationfunction is designed and manufactured and has the following beneficialeffects:

(1) The preparation device uses polymer-based particles as raw materialsand polymer-based spherical powder as a target product, and the preparedpolymer-based spherical powder has high sphericity, high flowability andnarrow particle size distribution and is applicable to the SLS field, sothe preparation device becomes a new way for continuous, large-scale andmass preparation of high-performance polymer-based spherical powder.

(2) The preparation device realizes ultra-fine pulverization of polymerparticles by using the mill milling system with the mills as a mainbody, and then performs spheroidization treatment of the milled powderby using a temperature field generated by inductive plasma. There arecomplete facilities for a preparation system, no solvent is involved inthe entire production process, and no pollutant is discharged, so thatthe preparation method is safe, environmentally friendly, clean andreliable.

(3) The preparation device has a wide application range and highadjustment ability, and the milling surface spacing, the air flow rate,the voltage size, the feeding pipe position and other process conditionscan be changed according to types and properties of the materials toproduce any type of thermoplastic polymers or spherical powder ofcomposite materials.

(4) The mill milling system of the preparation device realizesultra-fine pulverization of materials at room temperature by applying astrong extrusion, shearing and hoop stress to the materials. Theinductively coupled plasma powder spheroidization system useshigh-temperature plasma as a high-temperature heat source, so thatpolymer powder is heated uniformly, the melting and cooling rates arehigh, and spheroidization treatment can be completed in a very shorttime. The entire preparation method has the advantages of highproduction efficiency, low costs and short production cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a polymer-based sphericalpowder preparation device in Embodiments 1-3 of the present invention.

FIG. 2 is an electron micrograph of nylon 12 spherical powder preparedin Embodiment 1 of the present invention.

In the figures, 1 feeding hopper, 2 hydraulic machine, 3 fixed millcavity cover, 4 fixed mill water inlet, 5 fixed mill water outlet, 6fixed mill, 7 rotating mill, 8 rotating mill cavity cover, 9 rotatingbearing, 10 transmission chain, 11 motor, 12 rotating mill water inlet,13 rotating mill water outlet, 14 feeding pipe, 15 reaction gas inletpipe, 16 protective gas inlet pipe, 17 reaction gas pipe, 18 protectivegas pipe, 19 high-frequency power supply, 20 induction coil, 21collection chamber, 22 condensed water inlet pipe, 23 slurry outlet, 24vacuum pumping device, 25 inductively coupled plasma generator, 26cooling and shaping chamber, 27 high-pressure gas spray head, and 28molten material spray head.

DETAILED DESCRIPTION

The present invention is further described below by using theembodiments and the accompanying drawings. It is worth noting that thegiven embodiments should not be considered as limitations to theprotection scope of the present invention. Some non-essentialimprovements and adjustments made to the present invention by thoseskilled in the art based on the content of the present invention shouldstill fall into the protection scope of the present invention.

Embodiment 1

As shown in FIG. 1 , a polymer-based spherical powder preparation deviceincludes a mill milling system and an inductively coupled plasma powderspheroidization system.

The mill milling system includes a feeding hopper 1, a mill cavity covercomprising a fixed mill cavity cover 3 and a rotating mill cavity cover8, a fixed mill 6, a rotating mill 7, a rotating bearing 9, atransmission device comprising a transmission chain 10, a motor 11 and aliquid medium temperature adjustment system. The fixed mill 6 and therotating mill 7 are fixed in the fixed mill cavity cover 3 and therotating mill cavity cover 8 respectively. The rotating mill 7 isfixedly connected to the rotating bearing 9, and the transmission chain10 is driven by the motor 11 to drive the rotating bearing 9 to rotate,thereby driving the rotating mill 7 to rotate. The fixed mill 6 and therotating mill 7 are also provided with the liquid medium temperatureadjustment system, and the liquid medium temperature adjustment systemis liquid medium channels separately arranged in the fixed mill 6 andthe rotating mill 7 and a corresponding liquid medium circulationdevice. The rotating bearing 9 is separately provided with a rotatingmill water inlet 12 and a rotating mill water outlet 13 which arecommunicated with the liquid medium channel in the rotating mill. Theliquid medium channel in the fixed mill is separately communicated witha fixed mill water inlet 4 and a fixed mill water outlet 5 which areformed in a non-milling surface of the fixed mill, and the entire millmilling system is of a closed type.

The fixed mill 6 and the rotating mill 7 are fixedly connected to thehydraulic machine 2, and the milling surface spacing or pressure betweenthe fixed mill 6 and the rotating mill 7 is adjusted by using thehydraulic machine 2.

The inductively coupled plasma powder spheroidization system includes aninductively coupled plasma generator 25, a cooling and shaping chamber26, a collection chamber 21, a gas supply device, a high-frequency powersupply 19 and a vacuum pumping device 24, and the inductively coupledplasma generator 25, the cooling and shaping chamber 26 and thecollection chamber 21 are communicated with one another.

The inductively coupled plasma generator 25 includes a feeding pipe 14,a reaction gas pipe 17, a protective gas pipe 18, an induction coil 20,a molten material spray head 28 and a generator housing, the reactiongas pipe 17 is arranged in the protective gas pipe 18, one end of thefeeding pipe 14 is closely connected to a discharging end of the millmilling system, the other end of the feeding pipe penetrates through thereaction gas pipe 17 and extends into the protective gas pipe 18, theinduction coil 20 is arranged around an outside of the protective gaspipe 18, and the reaction gas pipe 17 does not extend into a surroundingsetting surface of the induction coil 20. The molten material spray head28 is arranged at a tip of the end, close to the induction coil 20, ofthe protective gas pipe 18, and a nozzle diameter of the molten materialspray head 28 is 13 mm. The reaction gas pipe 17, the protective gaspipe 18, the induction coil 20 and the molten material spray head 28 areall closely fixed in the generator housing, and the inductively coupledplasma generator 25 is communicated with the cooling and shaping chamber26 through the molten material spray head.

The feeding pipe 14 is also covered with a condensed water sleeve andthe feeding pipe 14 is also provided with a temperature measuringdevice.

A central axis of the reaction gas pipe 17 overlaps with a central axisof the protective gas pipe 18, and one ends of the reaction gas pipe andthe protective gas pipe are flush and fixed in the generator housing.The reaction gas pipe 17 is a straight pipe with a length of 60 mm and anozzle diameter of 35 mm, and the protective gas pipe 18 is a straightpipe with a length of 350 mm and a nozzle diameter of 55 mm.

A diameter of the feeding pipe 14 is 12 mm, the other end of the feedingpipe penetrates through the reaction gas pipe and extends into theprotective gas pipe, and a nozzle of the feeding pipe extending into theprotective gas pipe is 40 mm away from the reaction gas pipe, so thatthe polymer-based powder directly enters a target area of a plasma torchthrough the feeding pipe, and a temperature field of the target area is350° C.

The nozzle of the molten material spray head 28 overlaps with thecentral axis of the protective gas pipe 18, the molten material sprayhead 28 forms a convex structure toward the outside of the protectivegas pipe, and the nozzle is 20 mm away from the protective gas pipe.

The cooling and shaping chamber 26 includes high-pressure gas sprayheads 27 and a cooling and shaping chamber housing, there are 8high-pressure gas spray heads 27, and a cross section of the cooling andshaping chamber housing is circular. The 8 high-pressure gas spray headsare arranged around the circular cross section of the cooling andshaping chamber housing at equal distances, and the nozzles all face acircular center of the circular cross section. The circular center islocated on a central axis of the nozzle of the molten material sprayhead 28 and is 15 mm away from the nozzle.

The collection chamber 21 includes a condensed water inlet pipe 22, aslurry outlet 23 and a collection chamber housing, and the collectionchamber housing is communicated with the cooling and shaping chamberhousing.

The gas supply device includes a reaction gas inlet pipe 15 with one endcommunicated with the reaction gas pipe 17 and a protective gas inletpipe 16 with one end communicated with the protective gas pipe 18, andthe other ends of the reaction gas inlet pipe 15 and the protective gasinlet pipe 16 are communicated with the reaction gas pipe and theprotective gas pipe respectively.

The high-frequency power supply 19 is electrically connected to theinduction coil 20, and a high-frequency power supply with an outputfrequency of 3±0.5 MHz is used.

The vacuum pumping device 24 is communicated with an inside of thecooling and shaping chamber housing.

The generator housing, the cooling and shaping chamber housing and thecollection chamber housing are connected to one another and integrallyformed, a double-layer water-cooled stainless steel structure isadopted, and a cooling water inlet and outlet is formed in an outsidesurface.

A preparation method for preparing polymer-based spherical powder byusing the preparation device includes the following steps:

(1) milling: nylon 12 particles are weighed and put into the preparationdevice through a feeding hopper, and process parameters for the millmilling system are set as follows: a milling pressure is 10 MPa, arotating speed of a rotating mill is 35 r/min, and a temperature ofcooling water is 4° C.;

(2) spheroidization: reaction gas and protective gas are introducedthrough a reaction gas inlet pipe and a protective gas inlet piperespectively, high-pressure gas is introduced into a high-pressure gasspray head for spraying, and process parameters for an inductivelycoupled plasma powder spheroidization system are set as follows: areaction gas flow rate is 1.2 m³/h, a protective gas flow rate is 1.2m³/h, a voltage of a high-frequency power supply is 6400 V, an anodecurrent is 7 A, a frequency is 3±0.5 MHz, a flow rate of moltenmaterials at a nozzle is maintained at 4 V/s, a gas pressure in acooling and shaping chamber is maintained at 0.04 MPa, and a temperaturein a feeding pipe is controlled to be 50° C.;

(3) collection: condensed water is introduced through a condensed waterinlet formed in a collection chamber, and a slurry product flowing outof a slurry outlet is collected;

(4) post-treatment: the collected slurry product is filtered, dried andsieved to obtain nylon 12 spherical powder.

The reaction gas is argon, and the protective gas is argon.

The high-pressure gas is argon, and an introduced gas pressure is 1.5MPa.

The prepared nylon 12 spherical powder has a sphericity of 98% or above,an average particle size of 92.8 μm, a smooth particle surface with nowrinkles and burrs, narrow and normal particle size distribution, ahalf-peak width of 102 μm, a sintering window of 15.9° C., high powderflowability, and a stacking angle of 26°, and the nylon 12 sphericalpowder is applicable to SLS processing. Nylon 12 parts with dimensionalprecision of ±0.1% and density of 98% or above can be prepared by SLSprocessing.

FIG. 2 is a scanning electron micrograph of prepared nylon 12 sphericalpowder. It can be seen from characterization results that the preparednylon 12 powder is spherical in shape, smooth in surface and dense inmorphology and has no tail burrs or corner angles, so that the powder ishigh in flowability, high in bulk density, compact in powder bed andapplicable to SLS processing.

Embodiment 2

As shown in FIG. 1 , a polymer-based spherical powder preparation deviceincludes a mill milling system and an inductively coupled plasma powderspheroidization system.

The mill milling system includes a feeding hopper 1, a mill cavity covercomprising a fixed mill cavity cover 3 and a rotating mill cavity cover8, a fixed mill 6, a rotating mill 7, a rotating bearing 9, atransmission device comprising a transmission chain 10, a motor 11 and aliquid medium temperature adjustment system. The fixed mill 6 and therotating mill 7 are fixed in the fixed mill cavity cover 3 and therotating mill cavity cover 8 respectively. The rotating mill 7 isfixedly connected to the rotating bearing 9, and the transmission chain10 is driven by the motor 11 to drive the rotating bearing 9 to rotate,thereby driving the rotating mill 7 to rotate. The fixed mill 6 and therotating mill 7 are also provided with the liquid medium temperatureadjustment system, and the liquid medium temperature adjustment systemis liquid medium channels separately arranged in the fixed mill 6 andthe rotating mill 7 and a corresponding liquid medium circulationdevice. The rotating bearing 9 is separately provided with a rotatingmill water inlet 12 and a rotating mill water outlet 13 which arecommunicated with the liquid medium channel in the rotating mill. Theliquid medium channel in the fixed mill is separately communicated witha fixed mill water inlet 4 and a fixed mill water outlet 5 which areformed in a non-milling surface of the fixed mill, and the entire millmilling system is of a closed type.

The fixed mill 6 and the rotating mill 7 are fixedly connected to thehydraulic machine 2, and the milling surface spacing or pressure betweenthe fixed mill 6 and the rotating mill 7 is adjusted by using thehydraulic machine 2.

The inductively coupled plasma powder spheroidization system includes aninductively coupled plasma generator 25, a cooling and shaping chamber26, a collection chamber 21, a gas supply device, a high-frequency powersupply 19 and a vacuum pumping device 24, and the inductively coupledplasma generator 25, the cooling and shaping chamber 26 and thecollection chamber 21 are communicated with one another.

The inductively coupled plasma generator 25 includes a feeding pipe 14,a reaction gas pipe 17, a protective gas pipe 18, an induction coil 20,a molten material spray head 28 and a generator housing, the reactiongas pipe 17 is arranged in the protective gas pipe 18, one end of thefeeding pipe 14 is closely connected to a discharging end of the millmilling system, the other end of the feeding pipe penetrates through thereaction gas pipe 17 and extends into the protective gas pipe 18, theinduction coil 20 is arranged around the outside of the protective gaspipe 18, and the reaction gas pipe 17 does not extend into a surroundingsetting surface of the induction coil 20. The molten material spray head28 is arranged at a tip of the end, close to the induction coil 20, ofthe protective gas pipe 18, and a nozzle diameter of the molten materialspray head 28 is 15 mm. The reaction gas pipe 17, the protective gaspipe 18, the induction coil 20 and the molten material spray head 28 areall closely fixed in the generator housing, and the inductively coupledplasma generator 25 is communicated with the cooling and shaping chamber26 through the molten material spray head.

The feeding pipe 14 is also covered with a condensed water sleeve andthe feeding pipe 14 is also provided with a temperature measuringdevice.

A central axis of the reaction gas pipe 17 overlaps with a central axisof the protective gas pipe 18, and one ends of the reaction gas pipe andthe protective gas pipe are flush and fixed in the generator housing.The reaction gas pipe 17 is a straight pipe with a length of 80 mm and anozzle diameter of 40 mm, and the protective gas pipe 18 is a straightpipe with a length of 400 mm and a nozzle diameter of 60 mm.

A diameter of the feeding pipe 14 is 15 mm, the other end of the feedingpipe penetrates through the reaction gas pipe and extends into theprotective gas pipe, and a nozzle of the feeding pipe extending into theprotective gas pipe is 50 mm away from the reaction gas pipe, so thatthe polymer-based powder directly enters a target area of a plasma torchthrough the feeding pipe, and a temperature field of the target area is500° C.

A nozzle of the molten material spray head 28 overlaps with the centralaxis of the protective gas pipe 18, the molten material spray head 28forms a convex structure toward an outside of the protective gas pipe,and the nozzle is 30 mm away from the protective gas pipe.

The cooling and shaping chamber 26 includes high-pressure gas sprayheads 27 and a cooling and shaping chamber housing, there are 8high-pressure gas spray heads 27, and a cross section of the cooling andshaping chamber housing is circular. The 8 high-pressure gas spray headsare arranged around the circular cross section of the cooling andshaping chamber housing at equal distances, and the nozzles all face acircular center of the circular cross section. The circular center islocated on a central axis of the nozzle of the molten material sprayhead 28 and is 20 mm away from the nozzle.

The collection chamber 21 includes a condensed water inlet pipe 22, aslurry outlet 23 and a collection chamber housing, and the collectionchamber housing is communicated with the cooling and shaping chamberhousing.

The gas supply device includes a reaction gas inlet pipe 15 with one endcommunicated with the reaction gas pipe 17 and a protective gas inletpipe 16 with one end communicated with the protective gas pipe 18, andthe other ends of the reaction gas inlet pipe 15 and the protective gasinlet pipe 16 are communicated with the reaction gas pipe and theprotective gas pipe respectively.

The high-frequency power supply 19 is electrically connected to theinduction coil 20, and a high-frequency power supply with an outputfrequency of 3±0.5 MHz is used.

The vacuum pumping device 24 is communicated with an inside of thecooling and shaping chamber housing.

The generator housing, the cooling and shaping chamber housing and thecollection chamber housing are connected to one another and integrallyformed, a double-layer water-cooled stainless steel structure isadopted, and a cooling water inlet and outlet is formed in an outsidesurface.

A preparation method for preparing polymer-based spherical powder byusing the preparation device includes the following steps:

(1) milling: polyether-ether-ketone particles are weighed and put intothe preparation device through a feeding hopper, and process parametersfor a mill milling system are set as follows: a milling pressure is 15MPa, a rotating speed of a rotating mill is 50 r/min, and a temperatureof cooling water is 10° C.;

(2) spheroidization: reaction gas and protective gas are introducedthrough a reaction gas inlet pipe and a protective gas inlet piperespectively, high-pressure gas is introduced into a high-pressure gasspray head for spraying, and process parameters for an inductivelycoupled plasma powder spheroidization system are set as follows: areaction gas flow rate is 1.5 m³/h, a protective gas flow rate is 1.5m³/h, a voltage of a high-frequency power supply is 7000 V, an anodecurrent is 10 A, a frequency is 3±0.5 MHz, a flow rate of moltenmaterials at a nozzle is maintained at 5 V/s, a gas pressure in acooling and shaping chamber is maintained at 0.08 MPa, and a temperaturein a feeding pipe is controlled to be 70° C.;

(3) collection: condensed water is introduced through a condensed waterinlet formed in a collection chamber, and a slurry product flowing outof a slurry outlet is collected;

(4) post-treatment: the collected slurry product is filtered, dried andsieved to obtain polyether-ether-ketone spherical powder.

The reaction gas is argon, and the protective gas is argon.

The high-pressure gas is argon, and an introduced gas pressure is 2 MPa.

The prepared polyether-ether-ketone spherical powder has a sphericity of97% or above, an average particle size of 95.5 μm, a smooth particlesurface with no wrinkles and burrs, narrow and normal particle sizedistribution, a half-peak width of 108 μm, a sintering window of 16.1°C., high powder flowability, and a stacking angle is 24°, and thepolyether-ether-ketone spherical powder is applicable to SLS processing.

Polyether-ether-ketone parts with dimensional precision of ±0.1% anddensity of 98% or above can be prepared by SLS processing.

Embodiment 3

As shown in FIG. 1 , a polymer-based spherical powder preparation deviceincludes a mill milling system and an inductively coupled plasma powderspheroidization system.

The mill milling system includes a feeding hopper 1, a mill cavity covercomprising a fixed mill cavity cover 3 and a rotating mill cavity cover8, a fixed mill 6, a rotating mill 7, a rotating bearing 9, atransmission device comprising a transmission chain 10, a motor 11 and aliquid medium temperature adjustment system. The fixed mill 6 and therotating mill 7 are fixed in the fixed mill cavity cover 3 and therotating mill cavity cover 8 respectively. The rotating mill 7 isfixedly connected to the rotating bearing 9, and the transmission chain10 is driven by the motor 11 to drive the rotating bearing 9 to rotate,thereby driving the rotating mill 7 to rotate. The fixed mill 6 and therotating mill 7 are also provided with the liquid medium temperatureadjustment system, and the liquid medium temperature adjustment systemis liquid medium channels separately arranged in the fixed mill 6 andthe rotating mill 7 and a corresponding liquid medium circulationdevice. The rotating bearing 9 is separately provided with a rotatingmill water inlet 12 and a rotating mill water outlet 13 which arecommunicated with the liquid medium channel in the rotating mill. Theliquid medium channel in the fixed mill is separately communicated witha fixed mill water inlet 4 and a fixed mill water outlet 5 which areformed in a non-milling surface of the fixed mill, and the entire millmilling system is of a closed type.

The fixed mill 6 and the rotating mill 7 are fixedly connected to thehydraulic machine 2, and the milling surface spacing or pressure betweenthe fixed mill 6 and the rotating mill 7 is adjusted by using thehydraulic machine 2.

The inductively coupled plasma powder spheroidization system includes aninductively coupled plasma generator 25, a cooling and shaping chamber26, a collection chamber 21, a gas supply device, a high-frequency powersupply 19 and a vacuum pumping device 24, and the inductively coupledplasma generator 25, the cooling and shaping chamber 26 and thecollection chamber 21 are communicated with one another.

The inductively coupled plasma generator 25 includes a feeding pipe 14,a reaction gas pipe 17, a protective gas pipe 18, an induction coil 20,a molten material spray head 28 and a generator housing, the reactiongas pipe 17 is arranged in the protective gas pipe 18, one end of thefeeding pipe 14 is closely connected to a discharging end of the millmilling system, the other end of the feeding pipe penetrates through thereaction gas pipe 17 and extends into the protective gas pipe 18, theinduction coil 20 is arranged around an outside of the protective gaspipe 18, and the reaction gas pipe 17 does not extend into a surroundingsetting surface of the induction coil 20. The molten material spray head28 is arranged at a tip of the end, close to the induction coil 20, ofthe protective gas pipe 18, and a nozzle diameter of the molten materialspray head 28 is 10 mm. The reaction gas pipe 17, the protective gaspipe 18, the induction coil 20 and the molten material spray head 28 areall closely fixed in the generator housing, and the inductively coupledplasma generator 25 is communicated with the cooling and shaping chamber26 through the molten material spray head.

The feeding pipe 14 is also covered with a condensed water sleeve andthe feeding pipe 14 is also provided with a temperature measuringdevice.

A central axis of the reaction gas pipe 17 overlaps with a central axisof the protective gas pipe 18, and one ends of the reaction gas pipe andthe protective gas pipe are flush and fixed in the generator housing.The reaction gas pipe 17 is a straight pipe with a length of 50 mm and anozzle diameter of 30 mm, and the protective gas pipe 18 is a straightpipe with a length of 300 mm and a nozzle diameter of 50 mm.

A diameter of the feeding pipe 14 is 10 mm, the other end of the feedingpipe penetrates through the reaction gas pipe and extends into theprotective gas pipe, and a nozzle of the feeding pipe extending into theprotective gas pipe is 20 mm away from the reaction gas pipe, so thatthe polymer-based powder directly enters a target area of a plasma torchthrough the feeding pipe, and a temperature field of the target area is350° C.

A nozzle of the molten material spray head 28 overlaps with the centralaxis of the protective gas pipe 18, the molten material spray head 28forms a convex structure toward the outside of the protective gas pipe,and the nozzle is 10 mm away from the protective gas pipe.

The cooling and shaping chamber 26 includes high-pressure gas sprayheads 27 and a cooling and shaping chamber housing, there are 8high-pressure gas spray heads 27, and a cross section of the cooling andshaping chamber housing is circular. The 8 high-pressure gas spray headsare arranged around the circular cross section of the cooling andshaping chamber housing at equal distances, and the nozzles all face acircular center of the circular cross section. The circular center islocated on a central axis of the nozzle of the molten material sprayhead 28 and is 10 mm away from the nozzle.

The collection chamber 21 includes a condensed water inlet pipe 22, aslurry outlet 23 and a collection chamber housing, and the collectionchamber housing is communicated with the cooling and shaping chamberhousing.

The gas supply device includes a reaction gas inlet pipe 15 with one endcommunicated with the reaction gas pipe 17 and a protective gas inletpipe 16 with one end communicated with the protective gas pipe 18, andthe other ends of the reaction gas inlet pipe 15 and the protective gasinlet pipe 16 are communicated with the reaction gas pipe and theprotective gas pipe respectively.

The high-frequency power supply 19 is electrically connected to theinduction coil 20, and a high-frequency power supply with an outputfrequency of 3±0.5 MHz is used.

The vacuum pumping device 24 is communicated with an inside of thecooling and shaping chamber housing.

The generator housing, the cooling and shaping chamber housing and thecollection chamber housing are connected to one another and integrallyformed, a double-layer water-cooled stainless steel structure isadopted, and a cooling water inlet and outlet is formed in an outsidesurface.

A preparation method for preparing polymer-based spherical powder byusing the preparation device includes the following steps:

(1) milling: polyurethane particles are weighed and put into thepreparation device through a feeding hopper, and process parameters fora mill milling system are set as follows: a milling pressure is 10 MPa,a rotating speed of a rotating mill is 20 r/min, and a temperature ofcooling water is 0° C.;

(2) spheroidization: reaction gas and protective gas are introducedthrough a reaction gas inlet pipe and a protective gas inlet piperespectively, high-pressure gas is introduced into a high-pressure gasspray head for spraying, and process parameters for an inductivelycoupled plasma powder spheroidization system are set as follows: areaction gas flow rate is 1 m³/h, a protective gas flow rate is 1 m³/h,a voltage of a high-frequency power supply is 6000 V, an anode currentis 5 A, a frequency is 2.5 MHz, a flow rate of molten materials at anozzle is maintained at 3 V/s, a gas pressure in a cooling and shapingchamber is maintained at 0.02 MPa, and a temperature in a feeding pipeis controlled to be 40° C.;

(3) collection: condensed water is introduced through a condensed waterinlet formed in a collection chamber, and a slurry product flowing outof a slurry outlet is collected;

(4) post-treatment: the collected slurry product is filtered, dried andsieved to obtain polyurethane spherical powder.

The reaction gas is argon, and the protective gas is argon.

The high-pressure gas is argon, and an introduced gas pressure is 1 MPa.

The prepared polyurethane spherical powder has a sphericity of 98% orabove, an average particle size of 95.7 μm, a smooth particle surfacewith no wrinkles and burrs, narrow and normal particle sizedistribution, a half-peak width of 109 μm, a sintering window of 15.7°C., high powder flowability, and a stacking angle of 23°, and thepolyurethane spherical powder is applicable to SLS processing.Polyurethane parts with dimensional precision of ±0.1% and density of98% or above can be prepared by SLS processing.

What is claimed is:
 1. A polymer-based spherical powder preparationdevice, comprising a mill milling system and an inductively coupledplasma powder spheroidization system, wherein the mill milling systemcomprises a feeding member, a mill cavity cover, a fixed mill, arotating mill, a rotating bearing, a transmission device, a motor and aliquid medium temperature adjustment system; the fixed mill and therotating mill are fixed in the mill cavity cover, the rotating mill isfixedly connected to the rotating bearing, and the transmission deviceis driven by the motor to drive the rotating bearing to rotate, therebydriving the rotating mill to rotate; the fixed mill and the rotatingmill are also provided with the liquid medium temperature adjustmentsystem, the liquid medium temperature adjustment system realizestemperature adjustment of the fixed mill and the rotating mill byintroducing a liquid medium into the fixed mill and the rotating mill,and the mill milling system is of a closed type; the inductively coupledplasma powder spheroidization system comprises an inductively coupledplasma generator, a cooling and shaping chamber, a collection chamber, agas supply device, a high-frequency power supply and a vacuum pumpingdevice, and the inductively coupled plasma generator, the cooling andshaping chamber and the collection chamber are communicated with oneanother; the inductively coupled plasma generator comprises a feedingpipe, a reaction gas pipe, a protective gas pipe, an induction coil, amolten material spray head and a generator housing, the reaction gaspipe is arranged in the protective gas pipe, one end of the feeding pipeis closely connected to a discharging end of the mill milling system,the other end of the feeding pipe penetrates through the reaction gaspipe and extends into the protective gas pipe, the induction coil isarranged around the outside of the protective gas pipe, and the reactiongas pipe does not extend into a surrounding setting surface of theinduction coil; the molten material spray head is arranged at a tip ofthe end, close to the induction coil, of the protective gas pipe; thereaction gas pipe, the protective gas pipe, the induction coil and themolten material spray head are all closely fixed in the generatorhousing, and the inductively coupled plasma generator is communicatedwith the cooling and shaping chamber through the molten material sprayhead; the cooling and shaping chamber comprises a plurality ofhigh-pressure gas spray heads and a cooling and shaping chamber housing,the high-pressure gas spraying heads are arranged around a cross sectionof the cooling and shaping chamber housing at equal distances, nozzlesof the high-pressure gas spraying heads all face the same position inthe cooling and shaping chamber housing, and the position is located ona central axis of a nozzle of the molten material spray head; thecollection chamber comprises a condensed water inlet pipe, a slurryoutlet and a collection chamber housing, and the collection chamberhousing is communicated with the cooling and shaping chamber housing;the gas supply device comprises a reaction gas inlet pipe with one endcommunicated with the reaction gas pipe and a protective gas inlet pipewith one end communicated with the protective gas pipe, and the otherends of the reaction gas inlet pipe and the protective gas inlet pipeare communicated with the reaction gas pipe and the protective gas piperespectively; and the vacuum pumping device is communicated with aninside of the cooling and shaping chamber housing.
 2. The preparationdevice according to claim 1, wherein the mill milling system furthercomprises a hydraulic machine, the fixed mill and the rotating mill arefixedly connected to the hydraulic machine separately, and the millingsurface spacing or pressure between the fixed mill and the rotating millis adjusted by using the hydraulic machine.
 3. The preparation deviceaccording to claim 1, wherein the liquid medium temperature adjustmentsystem comprises liquid medium channels separately arranged in the fixedmill and the rotating mill and a corresponding liquid medium circulationdevice; the rotating bearing is separately provided with a liquid mediuminlet and a liquid medium outlet, and the liquid medium inlet and theliquid medium outlet are communicated with the liquid medium channel inthe rotating mill.
 4. The preparation device according to claim 1,wherein the feeding pipe is also covered with a condensed water sleeve;and the feeding pipe is also provided with a temperature measuringdevice.
 5. The preparation device according to claim 1, wherein acentral axis of the reaction gas pipe overlaps with a central axis ofthe protective gas pipe, and one ends of the reaction gas pipe and theprotective gas pipe are flush and fixed in the generator housing; thereaction gas pipe is a straight pipe with a length of 50-80 mm and anozzle diameter of 30-40 mm, and the protective gas pipe is a straightpipe with a length of 300-400 mm and a nozzle diameter of 50-60 mm. 6.The preparation device according to claim 1, wherein a diameter of thefeeding pipe is 10-15 mm, the other end of the feeding pipe penetratesthrough the reaction gas pipe and extends into the protective gas pipe,and the nozzle of the feeding pipe extending into the protective gaspipe is 20-50 mm away from the reaction gas pipe.
 7. The preparationdevice according to claim 1, wherein the nozzle of the molten materialspray head overlaps with a central axis of the protective gas pipe, themolten material spray head forms a convex structure toward an outside ofthe protective gas pipe, and the nozzle is 10-30 mm away from theprotective gas pipe.
 8. The preparation device according to claim 1,wherein there are 8 high-pressure gas spray heads, the cross section ofthe cooling and shaping chamber housing is circular, the 8 high-pressuregas spray heads are arranged around the circular cross section of thecooling and shaping chamber housing at equal distances, and the nozzlesall face a circular center of the circular cross section.
 9. Apreparation method for preparing a polymer-based spherical powder byusing the preparation device according to claim 1, comprising thefollowing steps: (1) milling: putting polymer-based particles into thepreparation device through a feeding member, and setting processparameters for a mill milling system as follows: a milling pressure is10-15 MPa, a rotating speed of the rotating mill is 20-50 r/min, and aliquid medium is cooling water with a temperature of 0-20° C.; (2)spheroidization: introducing reaction gas and protective gas through areaction gas inlet pipe and a protective gas inlet pipe respectively,introducing high-pressure gas into a high-pressure gas spray head forspraying, and setting process parameters for a inductively coupledplasma powder spheroidization system as follows: a reaction gas flowrate is 1-1.5 m³/h, a protective gas flow rate is 1-1.5 m³/h, a voltageof a high-frequency power supply is 6000-7000 V, an anode current is5-10 A, an output frequency is 3±0.5 MHz, a flow rate of moltenmaterials at a nozzle is maintained at 3-5 V/s, and gas pressure in acooling and shaping chamber is maintained at 0.02-0.08 MPa; (3)collection: introducing condensed water through a condensed water inletpipe arranged on the collection chamber, and collecting a slurry productflowing out of a slurry outlet; (4) post-treatment: filtering, dryingand sieving the collected slurry product to obtain polymer-basedspherical powder.
 10. The preparation method according to claim 9,wherein in the spheroidization step, a temperature in the feeding pipeis controlled to be 40-70° C.